Dispensers for sequentially dispensing multiple rolls of sheet material are generally known. U.S. Pat. No. 3,288,387 to Craven, for example, describes a sheet material dispenser that has a sensor for sensing the depletion of a first roll and a gripping member coupled with the sensor. The sensor is a roller that contacts the outmost winding of the first roll and is biased to move towards the center axis of the roll. When the first roll is entirely depleted, its core is exposed and the sensor roller moves into a groove in the core. This, in turn, causes the gripping member (via a linkage) to introduce the leading edge of the second roll into a feeding mechanism for dispensing. Unfortunately, the dispenser described in Craven is complex, has a high part count, and only works with “modified” roll cores (e.g., cores that have grooves or cavities).
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U.S. Pat. No. 3,628,743 to Bastian also describes a dispenser for sequentially dispensing multiple rolls of sheet material. Unlike, Craven, the diameter sensing roller and transfer mechanism in Bastian does not rely on a modified core. Instead, the dispenser senses a diameter size. The transfer mechanism components (e.g., rollers, linkages, springs) are configures such that an unwound portion of the second roll is introduced into a feeding mechanism once a predetermined minimum diameter is sensed. Like Craven, the dispenser in Bastian is complex, difficult to assemble, and has a high part count.
Other examples of dispensers with transfer mechanisms for sequentially dispensing multiple rolls of sheet material can be found in U.S. Pat. No. 4,165,138 to Hedge and U.S. Pat. No. 4,378,912 to Perrin. Both Hedge and Perrin describe a dispenser transfer mechanism that detects the absence of sheet material using a finger and a grooved roller that pinch an unwound portion of the first roll of sheet material. Once the first roll is depleted, the finger is allowed to enter the groove, causing a tucking device (via a linkage) to introduce the second roll of sheet material into a feed nip. Unfortunately, the finger and grooved roller introduces a significant amount of friction, making it difficult to dispense the first roll and increasing the likelihood of tearing. Furthermore, the tucking device remains between the feed mechanism after the second roll has already been fed through, which can interfere with the dispensing of the second roll of sheet material.
U.S. Pat. No. 5,526,973 to Boone, U.S. Pat. No. 7,698,980 to Morris, U.S. Pat. No. 6,354,533 to Jesperson, and U.S. Pat. No. 6,736,348 to Forman each describes a two-roll dispenser that includes a transfer mechanism that has a tucking device for introducing a second roll of sheet material into a feed mechanism. Unfortunately, these references also suffer from numerous drawbacks, including: low reliability and robustness; difficult to manufacture, assemble, and calibrate spring tension; and high part count.
Thus, there is still a need for improved dispensers for sequentially dispensing multiple rolls of sheet material.